Analysis determinative of gas or oil producing strata



May 24, 1960 K. H. SCHMIDT ANALYSIS DETERMINATIVE 0F GAS OR OIL PRODUCING STRATA Filed March 23, 1956 4 Sheets-Sheet 1 $595 $15 mo 92 wzomm om z $15 mom 322 mm oh mjmo N H H Um P62 538% w EZQEQ w x H565 209:6 m NM mzfinm v mzfiomm m m .n z QzN M7215 N n as? 52 5:25: ok 85:33 02 m6 mac w 8 356m 28 $02 58. 50 w- INVENTOR KARL H. SCHMIDT ATTORNEY y 4, 19 0 K. H. SCHMIDT 2,938,117

ANALYSIS DETERMINATIVE OF GAS OR OIL PRODUCING STRAIA Filed March 23, 1956 4' Sheets-Sheet 2 J1 VOLTAGE j in REGULATOR INFRA RED 7 29 GAS ABSORPTION CELL/ THERMO COUPLE 28 IST.

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32 INVENTOR RECORDER KARL H. SCHMIDT ATTORNEY May 24, 1960 K. H. SCHMIDT ANALYSIS DETERMINATIVE OF GAS OR OIL PRODUCING STRATA Filed March 23, 1956 4 Sheets-Sheet 3 GAS PUMP FIG. 3. 40

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INVENTOR KARL H. SCHMIDT ANALYSIS DETERMINATIVE 0F GAS OR OIL PRODUCING STRATA 4 Sheets-Sheet 4 Filed March 23, 1956 Jmm mum Fm 50 z- 0503 Oh m w "-0 0:4! zOEbDQOma ZOCHEGO. 50 mwwum m0 wOrwwEmh0 m IU INVENTOR KARL H. SCHMIDT 2 w co.

A TTORNE Y United States Patent ANALYSIS DETERMINATIV E OF GAS 0R OIL PRODUCING STRATA Karl H. Schmidt, East San Antonio, Tex., assignor to Petroleum Service and Research Corporation, San Antonio, Tex., a corporation of Texas Filed Mar. 23, 1956, Ser. No. 573,418

Claims. (Cl. 250-435) This invention relates to gas and oil well drilling and particularly to analytical methods such as logging, core sample analysis, drill stem test sample analysis, and the like, undertaken during or subsequent to the drilling of wells in the search for gas or oil, to determine the characteristics of the reservoir formation, usually sand or limestone, as determinative of its gas or oil producing characteristics. The invention is directed primarily to the foot by foot evaluation of porous reservoir strata as it is being penetrated, as in the case of well logging, or foot by foot evaluation as it is represented by cores or core samples, or by footage intervals as represented by drill stem testing. The evaluation obtained is as to the classification of the strata as gas, gas-condensate, or oil bearing, with delineation of fluid contacts such as gas-oil contact, gas-water contact, oil-water contact and the like within vertical sections of the strata. The invention is useful in an exploratory sense in predicting the proximity to sources of gas, gas-condensate, or oil in either a vertical direction in advance of a drill bit, or in a horizontal direction in an adjacent area. The invention is also useful on a regional scale for geologic identification and/or for correlative purposes.

The factors which determine the gas or oil yielding characteristics of strata are, principally, the nature of the fluid deposit, whether gas, gas-condensate or oil, saturating the formation, the productivity of the formation considered as a function of its permeability, and the pressures which exist within the strata or formation. It is recognized that all petroliferous bearing formations include water (Connate) saturation to some degree dependent upon the physical characteristics of the formation.

Prior methods for determining the nature of the deposits (petroliferous) within formations have not been 'reliable, so far as I am aware, partly because of the lack of sensitivity and/or inability of the analytical methods and equipment, such as the conventional hot-wire apparatus, for determining the nature of constituent gases of the gas stream delivered by the sample source.

In accordance with the present invention I measure accurately the constituent hydrocarbon gases, divorced from the combustible gas components other than hydrocarbons, and from these'constituent measurements I obtain precise ratios by which I am able to predict with exceptional success the nature of the substrata deposit.

The present invention provides a method and apparatus for hydrocarbon detection having a sensitivity which is much greater than current methods in use. The present invention offers a quantitative analysis for one or a plurality of different hydrocarbons.

Accordingly, an object of the present invention is to Patented May 24, 1960 provide a method and apparatus for Well logging wherein a quantitative analysis of hydrocarbons present is made to provide sufiicient data to predict, independent of other methods such as core analysis or electrical logging, that a sand will produce gas, oil or water.

Another object of the present invention is to provide a quantitative analysis method utilizing a plurality of analyzer cells incorporating infra-red spectrographic means, and in which the plurality of cells are sensitized for different hydrocarbons to give a complete quantitative analysis which is a definite means of locating gas or oil productive horizons.

A further object of the present invention is to provide a method and apparatus for gas composition analysis which can be continuously and automatically performed, or if desired individual sample analysis can be effected, with composition of the gases being the factors sought rather than the mere qualitative occurrence of unknown hydrocarbons.

A still further object of the present invention is to provide means for the detection of hydrocarbons by infrared analysis which is absolute in being quantitative, requires no air or oxygen, responds only to a particular hydrocarbon for which an individual analysis cell is sensitized, does not destroy the sample thus allowing check analysis, and when used in conjunction with a series of cells provides the required information independent of the magnitude of the combustible gas concentration. 5 i

Another and important object of the present invention is to provide a method and apparatus for the continuous analysis of gases derived from a mud stream or from well cuttings which is unique, not in the measurement of absorption by the use of a thermocouple particularly, but in the use of a bank of cells to provide a quantitative component gas analysis which is independent of the actual total quantity of gas available for analysis.

Accordingly, the present invention is utilized for det'ermining whether a formation is gas or oil productive. The original source of the gas, the formation penetrated by or below the drill bit, controls the composition and the quantitative ratios of the individual gases; gas, oil, and occasionally water sands releasing gas to the mud stream or retaining gas in the cuttings of different and characteristic composition ratios.

It will accordingly be seen that of the essence of the present invention is its ability to obtain sufiicient information by the analysis for several gases to provide sufficient data to predict, independent of other methods such as core analysis or electric logging, that a strata or medium will produce gas, oil or water and the method is continuous and utilizable both with a mud stream used in the drilling or with cuttings. When horizons are only partially penetrated, the method can also be utilized to advise the need for coring or drill stern testing when the data obtained by such procedures appears necessary.

It is a further object of the present invention to provide means whereby a continuous mud stream how is prepared for hydrocarbon analysis by apparatus in the nature of a gas trap for releasing gas from the mud stream.

A still further object of the present invention is to provide means for preparing cuttings included in a mud stream for continuous hydrocarbon content analysis since such cuttings contain a residual gas content which is held and absorbed by the cuttings themselves.

thereof.

Another object of the present invention is to provide such a continuous hydrocarbon content analysis of gases from mud streams and well cuttings in which recycling of the gas is permitted to establish stabilization of the quantities of the gas found to be present. This is permitted since gas, according to the present method, is not destroyed in any manner by the analysis and a complete continuous cycle can thereby be performed.

Additional o ects and advantages of the present invention will be c ent from the following detailed descrip tion of embo nts of the invention taken together with the accompanying drawings, in which:

Fig. l is a. diagrammatic view of the gas detection and analysis apparatus of the present invention showing a plurality of analyzing cells sensitized to diiferent hydrocarbons;

Fig. 2 is a schematic view of a single hydrocarbon gas analyzing or absorption cell including the electrical circuit for operation thereof;

Fig. 3 is a diagrammatic view of apparatus for treating a continuous mud stream flow to extract gases therefrom;

Fig. 4 is a diagrammatic view of apparatus for extracting gases from well cuttings;

Fig. 5 is a chart indicating the types of gases to which the individual gas analyzing chambers may be sensitized for complete quantitative analysis of hydrocarbon gases, and

Fig. 6 is a further chart to be referred to.

The apparatus and circuit shown in Fig. l are diagrammatic but serve to indicate the apparatus and function A gas to be analyzed is passed from the gas source which can be (a) mudstrearn gas trap, (19) cuttings, or (c) a core sample crusher. lvlanifestly, other sources of gas could be utilized and the block representation of a gas source is intended to include any and all such sources of which two will be more specifically hereinafter described. The gas to be analyzed passes from the gas source through pipe 1% and the flow is controlled by means of valve 11. A pump inserted in operative connection in pipe lit serves to force the gas under pressure into a bank or plurality of gas analysis cells generally indicated at 13.

The bank of gas analysis cells 13 includes, as shown in Fig. 1, six individual cells specifically designated 1, 2, 3, 4, 5, and 6, respectively. An inlet 14 is provided in the upper portion of each of these cells, and an outlet 15 is provided in proximity to the bottom of each of the cells. Gas passing from the gas source through the pipe and pump 12 will pass into cell i. and thereafter by means of pipes 16 interconnecting the outlets and inlets of contiguous or adjacent cells pass through the entire bank of cells L6, inclusive. The gas thereafter will be discharged into pipe 17 connected to the outlet of cell 6, the last one in the bank.

An exhaust line 18 connected into pipe 1'7 and controlled by valve 19 permits exhausting the analyzed gas to the atmosphere. The pipe 17 is then continued as pipe 20 controlled by valve 21 and serves as a recirculation conduit which is connected into pipe it between valve 11 and pump 12. In proximity to this connection point a control valve 22 is inserted. The purpose of the re-circulation line is to permit re-circulation of gases until equilibrium or a stabilization of the quantities of the gas found to be present is reached. it will be apparent that not only a continuous flow of gas can be analyzed, but also spot samples can be tested and checked.

The individual analyzing cells 1-6 inclusive are of a known type including a source of infrared waves or light 23 in the upper portion thereof and thermocouples 24 in the bottom thereof. in operation, the infra-red source creates infra-red light or waves which are focussed upon the thermocouples in the gas analysis cells. When gas to be analyzed is introduced into the cells, either as a continuous flow or as spot samples, and after stabilization of the frequency and temperature control of the cell itself, then if any hydrocarbon is present in the gas it will, as is well known, absorb a certain portion of the infra-red light thereby reducing the amount of infra-red rays concentrated on the thermocouple. This creates an unbalance in the electric output of the thermocouple.

As shown in Fig. 1, a power supply source 25 is used which feeds power into a voltage regulator. The power source is volt AC. The purpose of the voltage regulator, generally indicated 26, is to obtain a high degree of stability of voltage applied to the infra-red exciter. In actuality, a separate voltage regulator and power source is required for each analyzer cell. This will appear more clearly from Fig. 2 of the drawings wherein the voltage regulator 26 is connected to power source 25 and leads 27 pass to the infra-red exciter.

From the thermocouple 24 in the gas analyzer cell, leads connect to a first amplifier 28 which also derives source from the 110 volt AC. power source by means of leads 29. Current from the thermocouple 24, resulting from absorption of a certain portion of the infra-red light and the unbalance created in the electric output of the thermocouple is amplified in the first amplifier circuit. It is possible, and in some instances necessary, to use a multiplicity of steps or phases of amplification in the first amplifier circuit in order to obtain the proper step-up.

Following the first amplification the signal on the output side thereof is reintroduced into a second or secondary amplifier 30 by means of leads 37. The second amplifier. 30 is interconnected with leads 29 to draw its source of power from the power source 25. The second amplifier is utilized to obtain sufficient signal strength to actuate a recorder circuit. A multi-point recorder 32 receives the amplifier signal from the second amplifier it) by means of leads 33. This recorder circuit takes variations in the fiow of current and converts them into a mechanical action. it is the changes in the output of the thermocouple which are thus recorded. As shown in Fig. l the recorder 32 is preferably a multiple recorder and has individual stylus responding respectively to the output of the individual gas analysis cells 1-6 inclusive. The curves shown on chart 34 of the recorder correspond in reference character to the different cells and accordingly show the quantitative gas content as determined by each of the individual cells 1-6 inclusive.

Displacement of the recorder is calibrated quantitatively for the, percentage of absorbing gas present in each of the gas absorption cells. Calibration is performed with known gas quantities and has been found to be highly reliable in duplication of actual concentration of the hydrocarbons for which each particular cell is sensitized. As shown on the chart, Fig. 5, the different cells are sensitized to react to different hydrocarbons. As an example only, for purposes of illustration, and not to be considered as limiting, cell 1 is sensitized for methane; cell 2 for ethane; cell 3 for propane; cell 4 for butane; cell 5 for carbon dioxide and cell 6 can be sensitized for any other hydrocarbon or gas which it is felt might be present in a certain locality, dependent upon the samples being tested. In actuality the carbon dioxide cell plays no role in the hydrocarbon gas content analysis but is shown as a part of the analysis bank since in certain areas the gas is associated with petroleum deposits.

As hereinbefore set forth, means must be provided to extract gas from either a mud stream, well cuttings, or other suitable source to pass into the bank of gas analyzer cells. In Fig. 3 there is diagrammatically shown an arrangement which can be employed in the field for continuous analysis of a mud stream. In the continuous mudv stream analysis, the portion of the mud returned from the bottom of a drilling well is diverted into an on location laboratory and to a gas trap generally indicated 35 by means of conduit or pipe 36. Mud is pumped into the gas trap 35 under pressure through pipe 36. Due to ,fsrth iathisspc ificatien the increase in size of the trap with respect to the flow line, there is an effective reduction of pressure which thereby releases gas from the mud stream. In order to aid the release of the gas, a baffle arrangement indicated at 37 is inserted in the gas trap and this tends to spray the mud for effecting an increase in the surface area for gas release. The baffle can be of any desired type and provided with a plurality of openings or slits such as at 38. The liquid level of the mud stream in the gas trap is indicated at 39. A gas pump 40 is interconnected with the gas space 41 in the gas trap above the liquid level 39 by means of pipe 42.

The gas pump 40 is then interconnected with the inlet to the gas absorption cell 43 by means of pipe 44. It is to be understood that gas absorption cell 43 represents the first in a bank or series of absorption cells. The gas pump 40 maintains a vacuum above the mud or liquid level 39 of the trap and constitutes an additional aid in gas release. The gas thus obtained is passed through the pump and a small amount of pressure is available on the discharge side of the pump. The gas thereafter, as hereinbefore set forth, is introduced into the gas absorption cells for analysis. The gas, following passing through cell 43, would then be introduced into the next of the series or bank and continuing through each cell until complete analysis has been performed. It can then be discharged into the air. The mud discharged into the gas trap can be returned to the mud pit of the well, and is of no further use in the analysis itself. The mud discharge outlet from the gas trap 35 is shown at 45 and spills into the mud discharge container 46 and from thence passes through discharge pipe 47.

In tight stands and limestones residual gas content is held and absorbed by cuttings themselves. For this reason it is necessary quite frequently to perform analysis on the cuttings for gas content. In the event that well cuttings are to be used, then a different type of apparatus for extracting the gas and passing it into the various gas absorption or analyzing cells is used. An example is set forth diagrammatically in Fig. 4 wherein means are provided such as a container 48 into which are discharged cuttings, which after being pumped into the gas trap along with a mud stream are collected from the discharge side of the gas trap such as shown in Fig. 3. The cylindrical container 48 is, in one preferred embodi- -ment, of about 2 quart capacity. Approximately half of the volume available is filled with cuttings, as indicated at 49, and then Water is added to a level beneath 'the inlet opening of pipe 50 thereby providing a gas space 51 in the top of the container 48. An electric stirring device including a motor 52 and a shaft 53 which extends down in proximity to the bottom of the container 48 is utilized. Agitating and/or cutting means such as blade 54 is secured on the lowermost end of shaft 53 and is adapted to agitate the cuttings to break them up and help in the release of any gas which might be retained therein. After complete mixing, the stirring action is stopped and gas withdrawn from the upper gas space 51 of the chamber through pipe 55 and gas pump 56 which then, through pipe 57, passes the gas into a gas absorption cell 58 of the same nature as those shown in Figs. 1 and 2. The pump 56 constitutes a vacuum pump with pressure discharge into the gas analysis cell and thereafter pumps the gas through pipe 50 back into the container 48. Since the gas is not destroyed in any manner by analysis,

a complete continuous cycle can be performed as long as necessary to obtain stabilization of the quantities of the gas found to be present. This diagrammatic showing in Fig. 4 shows only a single cell but a complete analysis .of the gases would require the passing of the gas out of one cell to the next in the series, and so forth, until the complete analysis had been performed as previously set It will thus be seen that the present invention provides a method and apparatus for spectrographic analysis for hydrocarbon concentrations which is useful as an aid to interpretation and solving core analysis and well logging problems. The detection of hydrocarbons by infra-red analysis in the bank or series of gas analyzer or absorption cells is absolute since it it quantitative, requires no air or oxygen, responds only to the particular hydrocarbon for which the cell is sensitized, does not destroy the sample thus allowing check analysis and when used in conjunction with the other apparatus provides the required information independent of the magnitude of the combustible gas concentration. The gas composition analysis is continuously and automatically performed, while, if desired, individual sample analysis can be used, with composition being the factors sought, rather than the mere qualitative occurrence of unknown hydrocarbons. The magnitude of concentrations in the new procedure then becomes meaningful as a measure of permeability or flow capacity. The method also allows the addition of cells as desired for other specific gases, such as carbon dioxide, non-combustible, which in certain areas of the country is associated with gas and oil. The present invention provides for continuous analysis of gases derived from the mud stream, which in certain areas is of prime importance relative to the practical application of the logging method. It is also utilizable for analysis of gases derived from cuttings in a continuous analysis procedure.

In Fig. 6 I have shown a log-log chart where the curves or, in this instance, straight lines, represent certain component ratios of hydrocarbon gases plotted against producing gas to liquid hydrocarbon ratios measured in cubic feet per barrel. The curves represent the best average straight line for the range of hydrocarbon ratios plotted against actual producing gas-liquid ratios for known petroliferous reservoirs in the categories falling between oil and dry gas as shown. This chart has been compiled from hundreds of known petroliferous reservoir producing characteristics and the gas analyses related thereto.

In drilling an oil or gas well in accordance with the present invention, a sample significant of the strata in question is first obtained and then analysed for its constituent hydrocarbon gases. The sample may be taken from a drilling mud, a mixture of drilling mud and cuttings, cuttings alone, air drilling fiow stream, drill stem test fluid, or from cores or core samples. The extraction of hydrocarbon gases, as above described, may be either by a batch or by a continuous method, and the quantitative values of the component hydrocarbon gases are then measured, preferably in the manner described, although other methods such as mass spectrometry, or gas chromatography, or any accurate analysis method could be used. The quantities of hydrocarbon components are then converted to ratios, preferably using one of the lighter hydrocarbons as a common numerator and the other constituent hydrocarbons as the denominator and in practice I have obtained excellent results by using comparative ratios with the methane component as the numerator standard.

In the samples taken from oil producing strata the quantity of methane calculated in mol percentage is less and the quantity of ethane and higher molecular weight hydrocarbons is greater than the percentages of those hydrocarbon gases yielded by samples taken from strata containing gas-cap gas, gas-condensate, or dry gas. And, furthermore, the ratios based on methane of the hydrocarbon gas components taken from an oil bearing strata are smaller than the corresponding ratios of hydrocarbon gases taken from samples of other strata as above identified.

Thus comparing five samples representing the four types of strata fluid saturation above identified (one representing oil, one representing gas-cap gas, one representing gas-condensate, two representing dry gas) the gas analysis and hydrocarbon ratios are as follows:

Sample Number 1 2 3 4 5 Reservoir Depth (it) 4, 000 3, 100 6, 300 8, 200 5, 200 Type of Production." Oil Gas-Cap Conden- Gas Dry Gas Gas sate Gas-L1 Ratio (cu. it./

b. 370 11, 000 60, 000 Infinite 85. 12 92. 35 93. 78 97. 16 99. 51 6. 53 3. 82 2. 01 1. l 0. 40 3. 49 1.77 1.17 0. 36 0.09 2.13 0. 95 0.60 0. 17 0.00 Pentanes 1. 20 0. 50 0. 33 0. 05 O. 00 Heptanes l. 53 0.61 1. 21 1. 11 0.00 Hydrocarbon Ratios (Functions):

lliethanc/Ethane- 13.1 24. 2 32. 2 84. 5 248. 8 Methanol Propane 24. 4 52. 2 80. 2 270. 0 1, 105 7 Methane/Butancs. 40. 0 97. 2 156. 3 571. 5 Infin te Methanc/Pentanes. 70. 9 184. 7 284. 2 1, 043. 2 Infinite *Not measurable.

Referring to Fig. 6, the log-log chart coordinates the values of hydrocarbon ratios, in the values shown as ordinates, plotted against producing gas-liquid hydrocarbon ratios in cubic feet per barrel plotted as the abscissa. A strata yielding up to 2000 cubic feet of gas per barrel of liquid hydrocarbon is characterized as oil saturated, as indicated by the legend at the top of the chart, by which I mean that the strata contains, in proximity to the drill hole, oil bearing formation characteristics of an oil well, if its permeability characteristics are adequate for the required productivity. The range of 2,000 to 20,000 cu. ft. of gas per barrel of liquid hydrocarbon characterizes the strata as containing in proximity to the drill hole, gascap gas or gas associated with oil. The values of 20,000 to 1,000,000 cu. ft. of gas per barrel of liquid hydrocarbon characterizes the strata as containing condensate; between 20,000 and 100,000 cu. ft. per barrel considered as normal or rich condensate, and above 100,000 to 1,000,000 cu. ft. or barrel being considered as lean condensate. From 1,000,000 to an infinite number of cubic feet of gas per barrel of liquid hydrocarbon shows the strata contains dry to very dry gas.

Throughout the entire range of strata of all characteristics of liquid hydrocarbon yield, the known methane to ethane ratio of the hydrocarbon gases yielded by the samples varies anywhere from about 5 to about 250 (high est observed being 1106 for gas composed of only methane and ethane) and I have found that the strata has the characteristics suitable for an oil well when that ratio falls below 18 as a ratio value.

The overall range in the methane to propane ratios for all types of strata lies between the values of about 7 and about 1100 (may be infinite) and of this entire range only ratios of less than 37 are significant of the type of liquid hydrocarbon to constitute an oil well strata. Similarly the range of ratios of methane to the butanes extends from about to infinity of which a ratio of less than 60 is of interest as an oil well source and the range of methane to pentanes ratios, also extending from about 10 to infinity has only values of less than about 110 which are significant as indicating a source of oil.

Thus these ratios of the several gaseous hydrocarbons afford very limited ranges, out of much broader possible overall ranges, within which significant oil deposits are indicated and I have found that in utilizing these ranges I am able to predict with exceptional accuracy the nature of the reservoir formation in question as to its oil bearing characteristics.

Moreover I have found a further significant factor in the utilization of these ratios which additionally enhances the accuracy of the deduction made from the analyses. To illustrate, the analysis of sample No. 1 as given above, which was obtained, as is the case for all examples, after basic chart preparation, is typical of an oil well and demonstrates how gas ratios are employed to describe an it oil well formation and as will be shown there is a relationship to be observed between the several ratios for the sample. I have plotted on Fig. 6 the values of the several ratios as indicated by the points at the values of 13.1 on the methane-ethane curve, 24.4 on the methane-propane curve, 40.0 on the methane-butanes curve and 70.9 on the methane-pentanes curve. The average line connecting these points is very nearly straight and vertical leading downwardly to the abscissa value of 370 cu. ft. of gas per barrel of liquid hydrocarbon. Similarly I have plotted points for the four ratio values for sample No. 2 and again the average line connecting the points is very nearly a vertical straight line. Also the ratio values for each of samples No. 3, 4, and 5, when plotted and connected by a line have a vertical relationship. This straight vertical line relationship is present, I have found, in all sample analyses for the type of strata geologically associated with oil and gas deposits, and greatly enhances the accuracy of the sample analysis and the reliability of the deductions as to reservoir formation characteristics taken therefrom. It is apparent that by continuous application of the ratio evaluation method, on a foot by foot basis, as a strata is being penetrated, changes in the saturating and producible fluid content are detected and accurately delineated. Thus a strata containing gas, oil, and water, all within its thickness interval, may be so analyzed and the gas-oil and oil-water contacts (fluid interfaces) be located as to depth and position within the strata with exceptional accuracy.

I have found that when so plotted the ratios of hydrocarbons from a gas sample derived from a given strata fall in approximately a vertical line when plotted on a log-log graph affording, in addition to source classification, an exceptionally accurate measure of the producing gas to liquid hydrocarbon ratio to be realized from the strata in question.

A significant aspect of the straight line relationship between the ratios in terms of methane for a given sample when plotted on log-log coordinates is that it eliminates the need for values of hydrocarbon gases of higher molecular weight than the pentanes, since the four values of ratios on the basis of pentanes and lower molecular weight hydrocarbons, will adequately determine the vertical line. By so eliminating the need for values with reference to higher molecular weight hydrocarbons, I efiectively obviate problems in prior analytical techniques requiring values for the higher molecular weight hydrocarbons which were extremely difficult to obtain because of their trace quantities present and because of the errors that were further introduced by the calculations of normalizing to compensate for the dilution of the gas samples.

The basic curves shown on Fig. 6 have been made from values taken from a multitude of test sample ratios and may be used reliably in the manner above indicated for determining the gas source and ratio of gas to liquid hydrocarbon production from any new reservoir formation sought to be evaluated. The sample is removed and analysed as above indicated and the significant ratios in terms of methane calculated and applied to the chart-of Fig. 6. The value for the methane-ethane ratio is located on the methane-ethane ratio curve and the other values are located on their respective curves. It will be found that the points on these curves representing these ratio values can be represented by a line which is very nearly straight and vertical so that the values of the gas to liquid hydrocarbon ratio, significant of the reservoir formation under study, may be read directly. It will be understood, of course, that the boundary limitations as given on the chart to classify the gas source as oil hearing or gas bearing strata are typical but not absolute in value. For instance if the analytical ratios form a vertical straight line pointing to a producing gas-liquid ratio of 2000 or less the gas source is typically classified as oil. The 2000 ratio as a precisely limiting ratio is subject to some variation depending upon reservoir depth,

which affects reservoir pressure and temperature, liquid hydrocarbon character such as gravity which afiects gas solubility characteristics, and also to some degree by the geologic province or age and its effect on reservoir liquid composition.

My invention is not to be limited to the use of methane as the common standard in the ratios of hydrocarbon gases, as other ratios, such as those based on ethane or other values, or combination ratios, may serve as well. Nor is my invention to be limited to analysis for gas or oil well delineation, nor limited to foot by foot strata evaluation, as it may be used as well in prospecting for a source of hydrocarbon gas or liquid of desired components as is apparent.

I claim:

1.'In oil well drilling, the process which comprises obtaining compositions significant of the fluid saturating underground strata, treating said compositions in fluid suspension to free the gases contained therein, continuously passing infra-red energy through a stream containing all of the gas components so obtained from an infra-red energy source of pre-selected frequency, absorbing a portion of the infra-red energy emitted by said source by the methane components of said gas stream, determining the mol percentage of the methane content of the said gas stream by measuring the heating effect of the residual infra-red energy so transmitted, subsequently continuously passing infra-red energy through a stream of gases of the same constituency as said first stream from a second infra-red energy source of a second pre-selected frequency, absorbing a portion of the infra-red energy emitted by said second source by the ethane component of said gas stream, determining the mol percentage of the ethane content of the said gas stream by measuring the heating efiect of the residual infra-red energy so transmitted from said second source, subsequently continuously passing infra-red energy. through a stream of gases of the same constituency as said first stream from a third infra-red energy source of a third pre-selected frequency, absorbing a portion of the infra-red energy emitted by said third source by the propane component of said gas stream, determining the mol percentage of the propane content of the said gas stream by measuring the heating efiect of the residual infra-red energy so transmitted from said third source, and extracting oil from the strata with respect to which the ratio of methane to ethane is in the range of between about :1 and 18:1 and the ratio of methane to propane is in the range of from about 7:1 to about 37:1.

2. The process of determining the gas and oil producing characteristics of underground strata during an exploratory drilling operation which comprises substantially continuously obtaining compositions significant of the characteristics of the strata as penetration of the strata progresses, continuously treating said compositions to free the gases contained therein, producing a continuously moving stream of said gases, determining the mol percentageof the methane content of said stream by passing infra-red energy through the stream and measuring the transmissivity of the gas to infra-red energy of a frequency characteristic preselected for absorption by the methane component of the gas, determining the mol percentage of the ethane content of said stream by passing infra-red energy through said stream of the same constituency as the stream through which infra-red energy was passed for determining the methane component and measuring the transmissivity of the gas to infra-red energy of a frequency preselected for absorption by the ethane content of the said stream and locating oil by determining the strata with respect to which the ratio of methane to ethane is less than about 18.

3. The method as defined in claim 2, which also includes the step of determining the mol percentage of the said gas stream of at least one further lower alkane selected from the group consisting of propane and the hutanes by continuously passing infra-red energy through the said stream of the same constituency as the stream through which infra-red energy was passed for determining the methane and ethane components, measuring the transmissivity to infra-red energy of a frequency characteristic preselected for absorption by the said further lower alkane component of the stream and locating oil by also determining the strata with respect to which at least one of the alkane ratios obtains of methane to propane in the range of from about 7:1 to about 37:1 and methane to the butanes in the range of from about 10 to l to about 60:1.

4. The process of determining the producing characteristics of underground strata during an exploratory drilling operation which comprises substantially continuously obtaining compositions significant of the characteristics of the strata as penetration of the strata progrwses, continuously treating said compositions to free the gases contained therein, and producing a continuously moving stream of said gases, determining the mol percentage of the methane content of said stream by passing infra-red energy through the stream and measuring the transmissivity of the gas to infra-red energy of a frequency characteristic preselected for absorption by the methane component of the gas, determining the mol percentage of the ethane content of said stream by passing infra-red energy through said stream of the same constituency as the stream through which infra-red energy from said first source was passed for determining the methane component and measuring the transmissivity of the gas to infra-red energy of a frequency preselected for absorption by the ethane content of the said stream, and locating gas by determining the strata with respect to which the ratio of methane to ethane is greater than about 18:1.

5. The method as defined in claim 4, which also includes the step of determining the mol percentage of the said gas stream of at least one further lower alkane selected from the group consisting of propane and the butanes by continuously passing infra-red energy through the said stream of the same constituency as the stream through which infra-red energy was passed for determining the methane and ethane components, measuring the transmissivity to infra-red energy of a frequency characteristic preselected for absorption by the said further lower alkane component of the stream and locating gas by also determining the strata with respect to which at least one of the alkane ratios obtains of methane to propane of greater than about 37:1 and methane to butane of greater than about 60:1.

6. The method as defined in claim 2 in which said gas stream is passed in series through a succession of cells in one of which infra-red energy from one source is passed through the stream to determine the methane content and in another of which infra-red energy from a second source is passed through said stream for determining the ethane content, said method also including the step of pumping said gas stream through said cells in series under positive pressure.

7. The process of locating desired fluid characteristics of successive depthwise increments of the underground as a drilling operation progresses continuously downwardly, which comprises substantially continuously obtaining compositions significant of the characteristics of the strata as penetration of the strata progresses, continuously treatingsaid compositions to free the gases contained therein, forming a stream of said gases, advancing the said stream continuously through a succession of at least three testing stations, while maintaining a constant constituency of the stream in the several stations, at a rate of flow controlled to correlate the portion of the stream passing through any station with the foot-by-foot location from which the sample was extracted, testing the said stream for the concentration of its lower alkane components selected from the group consisting of methane, ethane, propane, the butanes, and the pentanes by determining the mol percentage of one lower alkane component of i said stream by passing infra-red energy through the stream at one station and measuring the transmissivity of the gas to infra-red energy of a frequency characteristic preselected for absorption by the said lower alkane component of the stream, determining the mol percentage of a second lower alkane component of said stream by passing infra-red energy through the stream at a second station and measuring the transmissivity of the gas to infra-red energy of a frequency preselected for absorption by the said second lower alkane component of the stream, determining the mol percentage of a third lower alkane component of said stream by passing infra-red energy through the stream at a third station and measuring the transmissivity of, the gas toinfra-red energy of a frequency preselected for absorption by the third said lower alkane component, determining the ratios of one lower alkane component to each of a plurality of other lower alkane components, and locating a desired underground fluid strata by said ratios.

8. Themethod as defined in claim 7, which also includes the step of recirculating the said stream through said stations until equilibrium has been established.

9. The process of locating fluid underground by testing the successive depthwise increments of the underground as an exploratory drilling operation progresses continuously downwardly, which comprises substantially continuously obtaining compositions significant of the characteristics of the strata as penetration of the strata progresses, continuously treating said compositions to free the gases contained therein, forming a stream of said gases, advancing the stream continuously through a testing zone, while maintaining constant the constituency of the said stream through said zone, at a rate of flow controlled to correlate the portion of the stream passing through the said zone with the foot-by-foot location from which the composition was extracted, determining the mol percentages of a plurality of the lower alkane components of said stream at said zone, the said lower alkane components being selected from the group consisting of methane, ethane, propane and the butanes, and

locating oil by determining the strata with respect to which at least one of the ratios of mol percentages obtains of methane to ethane in the range of from about 5:1 to about 1821, methane to propane in the range of from about 7:1 to about 37: 1, and methane to thebutanes in the range of from about 10:1 to about :1.

10. The process of locating fluid underground by testing the successive depthwise increments of the underground as an exploratory drilling operation progresses continuously downwardly, which comprises substantially continuously obtaining compositions significant of the characteristics of the strata as penetration of the strata progresses, continuously treating said compositions to free the gases contained therein, forming a stream of said gases, advancing the stream continuously through a testing zone, while maintaining constant the constituency of the said stream through said zone, at a rate of flow controlled to correlate the portion of the stream passing through the said zone with the foot-by-foot location from which the composition was extracted, determining the mol percentages of a plurality of the lower alkane components of said stream at said zone, the said lower alkane components being selected from the group consisting of methane, ethane, propane and the butanes, and locating gas by determining the strata with respect to which at least one of the ratios of mol percentages obtains of methane to ethane of greater than about 18:1, methane to propane of greater than about 37:1, and methane to the butanes of greater than about 60:1.

References Cited in the file of this patent UNITED STATES PATENTS 2,296,852 Horner Sept. 29, 1942 2,324,085 Horvitz et a1 July 13, 1943 2,462,995 Ritzmann Mar. 1, 1949 2,694,923 Carpenter Nov. 23, 1954 2,706,253 Hutchins et al Apr. 12, 1955 OTHER REFERENCES Van Wingen et al.-The Oil Weekly--November 27, 1944, pages 32, 33, 36 and 38. 

7. THE PROCESS OF LOCATING DESIRED FLUID CHARACTERISTICS OF SUCCESSIVE DEPTHWISE INCREMENTS OF THE UNDERGROUND AS A DRILLING OPERATION PROGRESSES CONTINUOUSLY DOWNWARDLY, WHICH COMPRISES SUBSTANTIALLY CONTINUOUSLY OBTAINING COMPOSITIONS SIGNIFICANT OF THE CHARACTERISTICS OF THE STRATA AS PENETRATION OF THE STRATA PROGRESSES, CONTINUOUSLY TREATING SAID COMPOSITIONS TO FREE THE GASES CONTAINED THEREIN, FORMING A STREAM OF SAID GASES, ADVANCING THE SAID STREAM CONTINUOUSLY THROUGH A SUCCESSION OF AT LEAST THREE TESTING STATIONS, WHILE MAINTAINING A CONSTANT CONSTITUENCY OF THE STREAM IN THE SEVERAL STATIONS, AT A RATE OF FLOW CONTROLLED TO CORRELATE THE PORTION OF THE STREAM PASSING THROUGH ANY STATION WITH THE FOOT-BY-FOOT LOCATION FROM WHICH THE SAMPLE WAS EXTRACTED, TESTING THE SAID STREAM FOR THE CONCENTRATION OF ITS LOWER ALKANE COMPONENTS SELECTED FROM THE GROUP CONSISTING OF METHANE, ETHANE, PROPANE, THE BUTANES, AND THE PENTANES BY DETERMINING THE MOL PERCENTAGE OF ONE LOWER ALKANE COMPONENT OF SAID STREAM BY PASSING INFRA-RED ENERGY THROUGH THE STREAM AT ONE STATION AND MEASURING THE TRANSMISSIVITY OF THE GAS TO INFRA-RED ENERGY OF A FREQUENCY CHARACTERISTIC PRESELECTED FOR ABSORPTION BY THE SAID LOWER ALKANE COMPONENT OF THE STREAM, DETERMINING THE MOL PERCENTAGE OF A SECOND LOWER ALKANE COMPONENT OF SAID STREAM BY PASSING INFRA-RED ENERGY THROUGH THE STREAM AT A SECOND STATION AND MEASURING THE TRANSMISSIVITY OF THE GAS TO INFRA-RED ENERGY OF A FREQUENCY PRESELECTED FOR ABSORPTION BY THE SAID SECOND LOWER ALKANE COMPONENT OF THE STREAM, DETERMINING THE MOL PERCENTAGE OF A THIRD LOWER ALKANE COMPONENT OF SAID STREAM BY PASSING INFRA-RED ENERGY THROUGH THE STREAM AT A THIRD STATION AND MEASURING THE TRANSMISSIVITY OF THE GAS TO INFRA-RED ENERGY OF A FREQUENCY PRESELECTED FOR ABSORPTION BY THE THIRD SAID LOWER ALKANE COMPONENT, DETERMINING THE RATIOS OF ONE LOWER ALKANE COMPONENT TO EACH OF PLURALITY OF OTHER LOWER ALKANE COMPONENTS, AND LOCATING A DESIRED UNDERGROUND FLUID STRATA BY SAID RATIOS. 